Plunger for Syringes and Syringes

ABSTRACT

A plunger for a syringe may include a plunger head for fluid dense limiting a fluid chamber of the syringe, and a piston rod fixed to the plunger head. The piston rod may be formed by several longitudinally extending axial webs that have an outwardly radial extension from the longitudinal axis and lead into a common crossing section. A free activation edge, which radially protrudes the radial extension, may be provided on the piston rod and engageable with a vibration activator of a hollow body of the syringe to emit an acoustic signal. A swinging arm body may be arranged between two axial webs and couple the activation edge with the crossing section such that in case of a vibration activation in an axial direction the swinging arm body has a radial swinging arm length between the activation edge and the crossing section of at least 40% of the radial extension.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims priority under 35 U.S.C.§ 121 to U.S. patent application Ser. No. 15/546,897, filed on Jul. 27,2017, and titled “Plunger for Syringes and Syringes” which claimspriority to and is the national stage application, filed under 35 U.S.C.§ 371, of International Application No. PCT/EP2016/051678, filed on Jan.27, 2016, which claims priority to German Patent Application No. 102015000999.0, filed on Jan. 27, 2015, the entire contents of each ofwhich are hereby incorporated herein by reference in their entirety forall purposes.

The present invention relates to a plunger for a syringe, particularlyan injection syringe. Thereby the plunger is formed in a way that itprovides a user with an acoustic and a haptic feedback in order tocommunicate the dispensed amount of fluid to the user when dispensing apredetermined amount of fluid. A conventional plunger for such a syringecomprises a plunger head for fluid dense limiting a fluid chamber of thesyringe, which is limited from the outside by a particularly cylindricalhollow body. The liquid is pushed out of the fluid chamber through theplunger, which densely passes the hollow body to a dispensing end of thesyringe, whereby it is important that a precise dispensing amount ispredetermined.

Visual markings on the hollow body characterize different dispensingvolumes, which correspond to certain amounts of fluid and thereforeprovide the user with a visual control over the dispensed amount ofliquid. Such syringes have the disadvantage that the syringe has to bepositioned in a visual field of the user. Further, this sort of dosing adesired amount of liquid presents a certain risk, because it can easilyhappen that too less or too much liquid is dispensed, even if anunrestricted view to the syringe is provided, because the position ofthe plunger, which corresponds to the marking, is frequently difficultto recognize because of the limited transparent material of the hollowbody. Providing the user with an additional haptic feedback regardingthe respective amount when dispensing the liquid overcomes thisdisadvantage. Hereto it is known to provide snapping or snatchingelements extending radially and being arranged on the hollow body or onthe plunger, which can snappingly be engaged with recesses or grooves.When inserting the plunger into the hollow body the elements of theplunger are in contact with the elements of the hollow body. Thiscontact is tactile to the user through an increased or decreasedresistance. Furthermore, it is known to enhance the haptic signal withan acoustic signal.

EP 2 289 393 A1 discloses a syringe with a hollow cylinder with markingson its outer surface, which correspond to different amounts of fluid.Additionally grooves are provided on the inner surface of the hollowcylinder at the axial height of the markings to which form the plungerhead of the plunger is adapted in a way that when engaging with thegrooves the plunger head snaps and provides the user with a hapticfeedback. This functional integration at the plunger head has thedisadvantage of a difficult and elaborate manufacturing of the plungerhead and of the hollow cylinder and often leads to a dysfunction of thesealed plunger head, which particularly in the field of medicinetechnology is to avoid.

From WO 2005/058169 A2 a syringe with feedback elements is known whichare arranged on the plunger as well as on the hollow cylinder to engagewith one another and to provide acoustic and haptic signals. Thefeedback elements are formed as protrusions. When engaging a resistancehas to be overcome at first, in order to provide an acoustic signal. Theshaping of the protrusions as knobs or noses leads to an increase anddecrease in resistance, so that a precise dosing is difficult. Further,the knob-form only provides a weak acoustic signal.

WO 2008/016381 A1 discloses a dosage device in form of a syringepursuant to the subject-matter. The syringe provides pointed acousticsignal impulses, in order to communicate a predetermined dispensingdosage. Hereto, the piston rod of the plunger comprises several inseries arranged encompassing ring-shaped protrusions, which are mountedon the axially passing edges of the axial webs, which build the pistonrod. The ring-shaped protrusion has a radial extension, which ismarginally bigger than an engaging element, which is arranged on anactuation flange of the hollow body. When inserting the plunger, thering-shaped protrusion engages with the engaging element, whereby theacoustic signal is provided. A so designed syringe only provides a weakacoustic signal, too, which can be missed in case of usage.

SUMMARY

It is therefore an object of the present invention to overcome thedisadvantages of the known prior art, particularly providing a plungerfor a syringe and a syringe with an enhanced haptic and acousticfeedback, particularly without effecting the functionality of thesyringe and/or increasing the manufacturing costs.

This object is solved by the features of claim 1. Thereafter, a plungerfor a syringe, particularly for an injection syringe is provided, whichcomprises a hollow body, which receives the plunger. The hollow body ofthe syringe defines a preferably cylindrical interior, whereby ahermetic sealing of the plunger is facilitated when dispensing theliquid. It is clear that other shapes of the interior of the hollow bodycan be provided as well. Particularly, according to the invention theplunger is designed to be upgradable for existing structures of thehollow body as long as the aspects according to the invention of theplunger are fulfilled. The plunger comprises a plunger head for fluiddense limiting a fluid chamber of the syringe, which is limited on oneaxial side by the plunger head through building a fluid dense slightbearing and particularly elsewhere exclusively by the hollow body, whichcomprises a dispensing opening at the end face opposite to the plungerhead. Further, the plunger has a piston rod, which is fixed to theplunger head, with an actuation section, which particularly is disposedon the diametrically opposite side of the plunger head and which issuitable for actuating the plunger for inserting into the hollow body.The piston rod consists of several axially extending axial webs, whichcan be arranged point symmetrically to each other in the radial crossingsection and particularly have a cross or a core shape. Depending onstability reasons at least three, particularly exactly three, four, six,eight axial webs can be provided in order to particularly set thestability of the structure of the piston rod. The number of the axialwebs can also be used for increasing the number of acoustic feedbacksignals, and therefore reducing the dispensing volume, in order todispense dosage units as precise as possible. The several axial webs areparticularly arranged point symmetrically to the axial longitudinal axisof the piston rod. The axial webs comprise a radial extension, whichmeasures from the axial longitudinal axis to an axial passing radial andedge of the respective axial web. The several axial webs radiallyinwardly extend from the axial passing radial end edge to the axiallongitudinal axis of the piston rod and lead into a common core orcrossing section, which particularly centrally receives the longitudinalaxis.

The piston rod further comprises at least one freely accessibleactivation edge, which radially protrudes over the radial extension ofthe several axial webs, and which when inserting the plunger, isengageable with a vibration activator, such that an acoustic signal isemitted. The acoustic signal is within an audible frequency range of atleast 20 Hz, particularly at least 100 Hz or 500 Hz, particularlybetween 2,000 Hz and 5,000 Hz. In order to enhance the acoustic signalpower, a swinging arm body is fixed between two axial webs on the pistonrod. The swinging arm body builds particularly at this radial end the atleast one free activation edge. According to the invention the swingingarm body structurally couples the at least one free activation edgedirectly with the core section of the piston rod providing that theswinging arm body and particularly thus also the at least one freeactivation edge comprise a radial swinging arm length between theactivation edge and the crossing section of at least 40%, 50% or 60% ofthe radial extension in case of a vibration activation of the at leastone free activation edge in an axial direction. The radial swinging armlength particularly results from considering the minimal radial distanceof the engaging section of the activation edge to the axial longitudinalaxis of the swinging arm length is measured from an external section ofthe core or crossing section of the axial webs to the radial externalactivation section of the activation edge. Preferably the radialswinging arm length of the swinging arm body is at least half the sizeof the mean radial extension. The at least one swinging arm body extendsfrom its activation edge directly through forming material of the pistonrod to the core section, so that this radially extending material bridgedirectly transfers the vibrations being initiated at the activation edgeto the crossing section without necessarily having to transfer thevibrations through the axial webs, eventually being structurally coupledwith the activation edge. This means that the activation edge canthoroughly be structurally coupled also with the adjacent axial webs.According to the invention a direct structural coupling between theactivation edge and the core section is realized material bindingthrough the swinging arm body.

The swinging arm body therefore extends, additionally to the axial webs,between the axial webs in a radial direction to the core section.

Should the axial webs consist of different radial extensions in certainembodiments of the piston rod the radial extension of the piston rodshall be determinable through a mean radial extension of the severalaxial webs. Along the swinging arm length between the activation edgeand the crossing section the respective swinging arm body isparticularly formed continuously out of full material, so that anactivating vibration can be transferred in a directly radial directionto the crossing section. Preferably, the swinging arm body is formed asa swinging plate between the axial webs.

Preferably, the piston rod can be formed by four pairwiseperpendicularly longitudinally extending axial webs. Thereby, the axialwebs lead into a central crossing section, which receives thelongitudinal axis, and limit in a circumferential direction pairwiseeach a swinging space with a triangular crossing section. The swingingspace serves as a resonance chamber for enhancing the acoustic signalemitted by the swinging arm body in a way that two adjacent swinging armbodies axially limit the swinging space in the longitudinal groove,which is limited by two axial webs. In a circumferential directionadjacent swinging spaces as well as in an axial direction adjacentswinging spaces can communicate which each other as longitudinal grooveson the axial webs and transition passages at the radial end of theswinging arm body can be formed. Preferably, the distance between twoswinging arm bodies is bigger than the respective swinging arm length,preferably mean swinging arm length of the swinging arm body.

The basic shape of the swinging arm body can be formed differentlyregarding a plurality of swinging arm bodies. The basic shape of aswinging arm body can also consist of a pin or a stick shape, which isparticularly cylindrical or has an angular crossing section. The stickor pin length extending from the crossing section corresponds to theswinging arm length. The absolute radial swinging arm length, whichdescribes a second essential dimension of the ability of the swingingarm body to swing, arises from the difference of the radial distance ofthe respective activation edge to the longitudinal axis and the radialdistance of the specific point on the crossing section to thelongitudinal axis.

In a preferred embodiment of the invention the swinging arm body has adisc-shaped or a plate-shaped basic form, which extends particularlymainly in a circumferential and radial direction. A swinging arm bodywith a plate or a disc form is insofar advantageous, as a swinging spacein an axial direction can be limited by the swinging arm body, wherebythe resonance behavior when generating and transferring an acousticsignal is improved. Preferably, the especially disc- or plate-shapedswinging arm body can structurally merge into both adjacent axial websexcept for a free axial edge of the axial webs and/or the swinging armbody can at least merge into one of the two axial webs except for thefree accessible axial edge of the axial webs and/or the swinging armbody is not connected with any of the axial webs extending from thecross or core section. The plate-shaped swinging arm body is thereforepreferably exclusively coupled with the crossing section, withoutaffecting the ability of the swinging arm body to swing because of theaxial webs.

In a preferred embodiment of the invention the plunger is produced fromone piece together with the piston rod, the plunger head, and theswinging arm body, whereby walls of the axial webs and particularlydisc-shaped walls of the swinging arm body having a substantially equaldimension.

Preferably, a plate-shaped swinging arm body comprises a substantiallycontinuous wall thickness and/or is oriented with regard to the axiallongitudinal axis of the piston rod such that said axis is perpendicularto the platewise extension of the swinging arm body. The axial webs aswell, particularly in a longitudinal direction can be arrangedperpendicular to the plate-shaped swinging arm body.

In an exemplary embodiment of the invention the swinging arm body has aplate-shaped form, which extends in a circumferentially direction aroundthe longitudinal axis, whose thickness is smaller than substantially thetwice, preferably is equal to the thickness of the plunger. Preferably,the thickness of the plate is in the area of the ideal wall thickness,which is between 0.7 to 1.3 times the thickness of the plunger.Preferably, the wall thickness is smaller than 2 mm, particularlybetween 0.5 to 1 mm.

In a further teaching of the invention the swinging arm body is producedfrom one piece together with the piston rod, particularly by injectionmolding with plastic, and/or built by several plate-sections that arearranged parallel to each other. Preferably, all components of theplunger are manufactured from one piece, particularly injection moldedfrom one plastic piece.

In a preferred embodiment of the invention in every particularlyfunnel-shaped longitudinal groove of the piston rod, which is formed bytwo adjacent axial webs, swinging arm bodies that are preferablyplate-shaped, particularly shaped in plate sections are arranged inseries one behind another. The series of swinging arm bodies arepreferably identically structured and extend having a plate-shaped basicform parallel to each other. The axial distances of the plates to eachother are preferably identical but may also continuously get bigger orsmaller according to a regulation of the dispensing volume.

Preferably, two in a circumferential direction adjacent rows of severalswinging arm bodies are offset to each other in an axial direction,wherein the axial offset is continuously the same size. In a preferredembodiment of the invention the swinging arm bodies of two diametricallyopposite rows are axially exactly opposite to each other, so thatparticularly oppositely arranged swinging arm bodies of a plate shapedswinging arm body are arranged on a common radial plane.

The plunger preferably comprises in axial direction a length in therange of at least 50 mm and 150 mm, particularly between 60 mm and 105mm. A plunger head diameter is preferably between 5 mm and 30 mm,particularly between 9 mm and 20 mm. A swinging arm free end section ofthe plunger, which is related to the plunger head, extends in an axialdirection preferably beyond 10 mm, particularly at least 15 mm, and lessthan 35 mm, particularly less than 30 mm. A swinging arm body free frontsection of the plunger heading the actuating section comprises an axialextension of preferably at least 15 mm and less than 35 mm, particularlyat least 20 mm and less than 30 mm. The in circumferential directionadjacent rows of several swinging arm bodies comprise at least two,particularly five, particularly less than 15, swing arm bodies, whichhave an axial distance in the range from 5 mm to 25 mm, particularly 6mm to 17 mm, to each other.

In a preferred embodiment of the invention the at least one activationedge extends in a circumferential direction particularly shaped incircular sections and/or over a sector angle α of less than 100°,preferably 95° or 90°, preferably between 5° and 90°, preferably between10° and 60°. In an alternatively embodiment of the invention the axiallydefined activation edge can uninterruptedly completely circulate andthereby particularly describe a circular path. However, the activationedge can also comprise particularly radial inwardly displaced areasdifferent to the circle path when having a continuous progression, sothat only a certain section of the circulating activation edge can beengaged with the vibration activator of the hollow body. Particularly, aactivation edge in sections can be advantageous for a circulatingvibration activator at the hollow body.

It is clear that each activation edge or every pair of activation edgeson the same axial height corresponds to an acoustic signal for apredetermined dispensing amount of the syringe.

In a further embodiment of the invention at least two activation edgesare particularly structurally separated from each other arranged on thesame axial position of the piston rod, wherein particularly the at leasttwo activation edges having the same axial position are in sectionssubstantially diametrically opposite to each other and/or are shaped incircular sections with the same circumferential extension. This supportsa self-centering effect of the piston rod within the hollow body so thata plunger can be moved within the hollow body. The at least twoactivation edges are realized by two separate swinging arm bodies, infact by its radial end sections, wherein particularly the two swingingarm bodies are structurally separated from each other, particularlyseparated from each other by axial webs.

In an exemplary embodiment of the invention the axial webs extend beyondadjacent areas of the swinging arm body, wherein particularly these stepback areas have a smaller radial extension than the adjacent activationedge, in which the step back areas merge. Therefore, the step back areasdo not serve as an activation edge and cannot be engagable with thevibration activator of the hollow body.

Further, the invention relates to a syringe, particularly to aninjection syringe, particularly a medical injection syringe, whichcomprises a hollow body, and a plunger according to one of the precedingembodiments.

The hollow body particularly has a radial inwardly extending, preferablycompletely circumferential vibration activator, which for example isformed as a nose or a protrusion, which is positioned completely withinthe interior of the hollow body. Preferably, the vibration activator hasa cone-shaped or funnel-shaped input area, whose inclination is lessthan 10° with regard to the longitudinal direction. The vibrationactivator can have a non-declined, particularly cylindrical slidingsurface subsequent to the inclined activation chamber, wherein a profilejump, which is radially outwardly directed, follows the sliding surface,in order to obtain a free oscillation of the at least one activationedge.

In a further embodiment of the invention the swinging arm body of thepiston rod and the vibration activator of the hollow body are designedwith a radial oversize to each other, preferably between 0.05 to 2.0 mm.The radial oversize particularly depends on the dimensions of thesyringe itself. Syringes with big radial dimensions have an oversizebetween 0.5 to 2.0 mm, while narrower syringes have an oversize of lessthan 0.5 mm, particularly less than 0.1 mm. In an advantageousembodiment the inner diameter of the oscillation of the hollow body canbe 15.55±0.05 mm and the outer diameter of the vibration activator ofthe plunger can be 15.70±0.05 mm. Thus, the swinging arm body is excitedto oscillate by the activation edge, in order to emit an acousticsignal.

In a further embodiment of the invention an axial length of thevibration activator of the hollow body is aligned with the axialdistance of two axial adjacent swinging arm bodies such, that the twoadjacent swinging arm bodies are in engagement with the vibrationactivator. This has the advantage of a good guiding of the plungerwithin the hollow body and a tilting of the plunger head can be avoided.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following further features, characteristics and advantages of thepresent invention will become more readily apparent in view of thefollowing detailed description of the currently preferred embodimentsand accompanying drawings, which show:

FIG. 1 a perspective view of a first embodiment of the plunger accordingto the invention;

FIG. 2 a perspective view of an enlarged section of a piston rod of theplunger according to FIG. 1,

FIG. 3 a perspective view of a second embodiment of the plungeraccording to the invention;

FIG. 4 a perspective view of an enlarged section of the piston rod ofthe plunger according to FIG. 3;

FIG. 5 a perspective view of a third embodiment of the piston rod of theplunger;

FIG. 6 shows a side view of the plunger according to FIG. 5;

FIG. 7 a perspective view of an enlarged section of four swinging armbodies of the plunger according to FIGS. 5 and 6;

FIG. 8 a cross sectional view of the third embodiment of the plungeraccording to the invention;

FIG. 9 an enlarged section of a hollow body; and

FIG. 10 a schematic illustration of the functionality of the invention.

DETAILED DESCRIPTION

FIGS. 1 and 2 relate to a first embodiment of the plunger 1. The plunger1 thus comprises a piston rod 3, at whose one end a plunger head 2 andat whose other end an activation section 4 is positioned. The piston rod3 is built by four pairwise perpendicular axial webs 5. The axial webs 5merge into a common central cross or core section 6, which receives thelongitudinal axis. FIG. 2 shows an enlarged view of two of the parallelon the piston rod 3 arranged circumferentially extending swinging armbodies 8. The swinging arm bodies 8 comprise of a completelycircumferentially disc- or plate-shaped basic form and also a completelycircumferential activation edge 7, at whose radial outwardly pointingedge. The radial distance of the swinging arm bodies 8 to thelongitudinal axis 12 is thus bigger than the radial distance of theaxial webs 5 to the longitudinal axis 12 of the plunger 1.

In FIG. 1 several, particularly more than three swinging arm bodies,preferably in this example five swinging arm bodies are arrangedparallel to each other having a certain distance to adjacent swingingarm bodies 8 on the piston rod 3, which limit five resonance chamberswithin the hollow body 9 of the syringe.

Two perpendicular to each other arranged axial webs 5, and adjacent toeach other, form a longitudinal groove of the piston rod 3. At thebottom of the longitudinal groove, thus at the deepest positionregarding a radial direction, the transition area between the two axialwebs 5 is rounded. As can be seen in FIG. 8, a swinging arm length r_(S)is defined as a radial distance of the free activation edge 7. Further,it can be seen that the actuation section 4, which is fixed parallel tothe swinging arm bodies 8 of the piston rod 3, comprises a bigger radialdistance to the longitudinal axis 12 of the piston rod. In FIGS. 1 and 2a small radial oversize of the activation edge 7 with regard to thelongitudinal edge of the axial webs 5 is not further indicated, however,it is clear that the vibration activator 10 of the hollow body 2 ismeasured relative to the radial dimensions of the axial webs and theswinging arm bodies 8, respectively the activation edge 7 such that asnapping engagement is exclusively built between the vibration activator10 and the respective activation edge 7.

When inserting the plunger 1 according to the invention into anexemplary in FIG. 9 or 10 illustrated hollow body, which, however, canalso be formed as a conventional hollow body with an inwardly extendingactivation nose, the swinging arm bodies 8 engage with the activationnose and are activated to oscillate in an axial direction, whereby anaudible sound is realized through vibration activation of theplate-shaped swinging arm body 8.

The distance between two adjacent disc-shaped swinging arm bodies 8defines the volume unit, whose complete dispension produces an acousticsignal. Naturally, the predetermined amount of fluid, for which anacoustic signal should be emitted, can be set through reducing the axialdistance between two disc-shaped swinging arm bodies.

In FIGS. 3 and 4 perspective views of the second embodiment of theinvention are shown. For a better readability of the description of thefigures the same reference signs as in the embodiment according to FIGS.1 and 2 are used for similar or identical components of the plungeraccording to the invention. According to FIGS. 3 and 4 the plunger 1differs from the embodiment according to FIGS. 1 and 2 such that theswinging arm body is contactless with regard to one of the adjacentaxial webs 5. One axial web is separated from the swinging arm bodythrough a gap. On each half of the piston rod a pair of swinging armbodies 8 is arranged, wherein each swinging arm body substantiallybuilds a quarter disc.

At each predetermined axial position a pair of substantially identical,in a circumferential orientation of substantially 180° extending, plate-or disc-shaped swinging arm bodies 8 are arranged on the piston rod. Theswinging arm bodies 8 are fixed to the plunger 1 such that two firstopposite axial webs 5 are connected with the swinging arm bodies and twosecond opposite axial webs each have a distance to the swinging armbodies 8, so that a free space 21 between the second axial webs 5 andthe swinging arm bodies 8 in a radial direction is formed.

FIGS. 5 to 8 relate to a third embodiment of the plunger 1 according tothe invention. For an easy readability of the description of the figuresthe same reference signs shall be used for identical or similarcomponents of the plunger 1. The piston rod 3 forms at one axialposition two structurally in a circumferential direction separatedactivation edges 7, which are arranged separately diametrically oppositeto each other and comprise the same circumferential extension.

As can be seen in FIGS. 5 and 6, two in a circumferential directionadjacent swinging arm bodies 8 are arranged axially offset to eachother. The axial offset is substantially equal to half of the distancebetween two in an axial direction adjacent swinging arm bodies 8, whichare disposed in a row within the longitudinal groove of the piston rod3. Thus, the number of acoustic signals can be doubled and the dosingamount for each acoustic signal is reduced.

It is clear that through a reproduction of the longitudinal grooves bymore than four axial webs 5 a further potential of increasing theacoustic signals regarding one push stroke of the plunger 1 can beachieved. The swinging arm body comprises both of a disc sector form anda sectorwise activation edge 7, whose circumferential extension is lessthan 45°. In FIG. 8 the sectorwise form of the activation edge 7 of theswinging arm bodies 8 can be seen. Here, the swinging arm body 8comprises a circumferentially over the sector angle α extendingactivation edge 7, and in the further progression two substantiallystraight setback edges 23, which are not in engagement with thevibration activator 10 of the hollow body 9. The setback edges 23 passperpendicular to the axial longitudinal direction L and lead into arecess 25, which is incorporated into the axial edge of the axial webs5, in order to enable a transmission of signal oscillations between eachof the resonance chambers limited by the swinging arm bodies 8.

In FIG. 8 the radial distance of the axial webs 5 to the longitudinalaxis 12 of the plunger respective the plunger radius r_(K) is shown.Further, the swinging arm length r_(S), which radially inwardly extendsfrom the activation edge 7 to the core section 6, particularly to therounded bottom of the axial groove 5, is clearly bigger than the half ofthe mean radial extension r_(K), whereby a clear reinforcement of theacoustic power of the swinging arm body 8 is realized.

In FIG. 9 a geometric embodiment of the vibration activator 10 of thehollow body 9 of the syringe according to the invention is shown. Theradial circumferential vibration activator 10 is arranged on the innersurface of the hollow body 9 and comprises a lead-in input area 14 witha phase angle β₁ and a lead-out profile step 15 with a phase angle β₂,wherein β₁ is clearly smaller than β₂. The phase angle β₁ is preferablyunder 20°, wherein the phase angle β₂ is bigger than 25°.

In FIG. 10 a schematic diagram is shown to clarify the functionality ofthe invention. The plunger 1 is hereby inserted into an opening of thehollow body 9, in order to dispense fluid, which is located in theinterior of the hollow body 9. It can be seen that between the swingingarm bodies 8, arranged on the piston rod 2, and the vibration activator10 of the hollow body 9 an oversize is built. Thus, firstly, anincreased resistance has to be overcome when inserting, until at the endof the engagement process between one swinging arm body 8 and thevibration activator 10 the swinging arm body 8 slides from the vibrationactivator 10, wherein the resistance quickly reduces and the swingingarm body 8 emits an acoustic signal, particularly a click noise, throughcompensating the elastic deformation of the swinging arm body 8 duringthe engagement process. The swinging arm body 8 (swinging plate), whichradially continuously interruption-free, without a gateway or anopening, extends from the core section 6 maintains an extended swingingarm length r_(S) according to the invention, whereby the oscillationsignal is clearly increased when activated through an vibrationactivator. The swinging arm length r_(S) regarding a radial directionis, without considering the axial webs, clearly enlarged with regard tothe prior art.

The features disclosed in the above description, the figures and theclaims may be significant for the realisation of the invention in itsdifferent embodiments individually as in any combination.

1. A plunger for a syringe, which comprises a hollow body receiving theplunger, comprising a plunger head for sealing a fluid chamber of thesyringe, and a piston rod fixed to the plunger head with an actuationsection, at which the plunger can be actuated for inserting into thehollow body, wherein the piston rod is formed by axial webs extendingalong a longitudinal axis of the plunger, the axial webs having anoutwardly radial extension r_(K) from the longitudinal axis and leadinto a common crossing section, which receives the longitudinal axis,wherein at least one free activation edge, which radially protrudes theradial extension r_(K), is provided on the piston rod, which wheninserting the plunger, is engageable with a vibration activator of thehollow body such that an acoustic signal is emitted, characterized inthat a swinging arm body arranged between two axial webs couples theactivation edge with the crossing section such that in case of avibration activation in an axial direction the swinging arm bodycomprises a radial swinging arm length rS between the activation edgeand a crossing section of at least 40% of the radial extension r_(K). 2.The plunger according to claim 1, characterized in that the swinging armbody comprises a disc- or plate-shaped form, which extends in acircumferential direction and/or the swinging arm body structurally,except one free axial edge of the axial webs, merges into both axialwebs and/or swinging arm body only merges into one of the both adjacentaxial webs except one free axial edge of the axial webs and/or theswinging arm body is not connected to any of the axial webs.
 3. Theplunger according to claim 1, characterized in that the swinging armbody comprises a circumferentially around the longitudinal axisextending plate-shaped form, whose thickness is smaller thansubstantially two times the thickness of the plunger.
 4. The plungeraccording to claim 1, characterized in that the swinging arm body isproduced from one piece with the piston rod by injection molding withplastic and/or that the swinging arm body is formed by severalplate-sections that are arranged parallel to each other.
 5. The plungeraccording to claim 1, characterized in that the at least one freeactivation edge extends in a circumferential direction particularlyshaped in circular sections and/or the at least one free activation edgeextends in a circumferential direction with a sector angle α of lessthan 100°.
 6. The plunger according to claim 1, characterized in that atleast two activation edges are separately arranged on the same axialposition of the piston rod, wherein the at least two activation edges ofa same axial position are in sections diametrically opposite to eachother and/or shaped in circular sections with a same circumferentialextension.
 7. The plunger according to claim 2, characterized in thatthe axial webs radially protrude from the disc- or plate-shaped swingingarm body in an area of the sections of the axial webs adjacent to theaxial webs, which are formed without an activation edge.
 8. A medicalinjection syringe, comprising the hollow body and the plunger accordingto claim
 1. 9. The plunger according to claim 1, characterized in that aradial overlap exists between the swinging arm body of the piston rodand the vibration activator of the hollow body so that the swinging armbody gets into radial engagement with the vibration activator whenaxially moving the plunger into the hollow body.
 10. The plungeraccording to claim 9, characterized in that an axial length of thevibration activator of the hollow body is designed with regard to anaxial distance between two axially adjacent swinging arm bodies in sucha way that the two adjacent swinging arm bodies are in engagement withthe vibration activator.
 11. The plunger according to claim 10,characterized in that two in circumferential direction adjacent rows ofseveral swinging arm bodies are offset in axial direction, wherein theaxial offset is continuously the same size, wherein the axial offset issubstantially equal to half of a distance between two in axial directionadjacent swinging arm bodies.
 12. The plunger according to claim 5,characterized in that the swinging arm body comprises acircumferentially over the sector angle α extending activation edge, andin the further progression two substantially straight setback edges,wherein the setback edges are not in engagement with the vibrationactivator and/or pass perpendicular to an axial longitudinal directionand/or lead in a recess that is incorporated into the axial web.
 13. Theplunger according to claim 1, wherein the swinging arm body comprises acircumferentially around the longitudinal axis extending plate-shapedform, with a thickness of the plate-shaped form that is smaller thansubstantially one time a thickness of the plunger.
 14. The plungeraccording to claim 1, wherein the at least one free activation edgeextends in a circumferential direction particularly shaped in circularsections and/or the at least one free activation edge extends in asecond circumferential direction with a sector angle α of less than 90°.15. The plunger according to claim 1, wherein the at least one freeactivation edge extends in a circumferential direction particularlyshaped in circular sections and/or the at least one free activation edgeextends in a second circumferential direction with a sector angle α ofbetween 5° and 90°.
 16. The plunger according to claim 1, wherein the atleast one free activation edge extends in a circumferential directionparticularly shaped in circular sections and/or the at least one freeactivation edge extends in a second circumferential direction with asector angle α of between 10° and 60°.
 17. The plunger according toclaim 1, wherein a radial overlap exists between the swinging arm bodyof the plunger and the vibration activator of the hollow body of between0.05 mm to 0.5 mm, so that the swinging arm body gets into radialengagement with the vibration activator when axially moving the plungerinto the hollow body.